Scientists have uncovered a more complex atomic arrangement in superionic water, a form that likely powers the magnetic fields of Uranus and Neptune. This exotic state emerges under extreme pressures and temperatures, conducting electricity like a partial liquid within a solid framework. The discovery, from lab experiments mimicking planetary interiors, challenges prior models and refines understanding of ice giants.
Water transforms dramatically under the intense conditions inside giant planets, becoming superionic—a phase where oxygen atoms form a fixed lattice while hydrogen ions roam freely, enabling electrical conductivity. This property makes superionic water a prime suspect for generating the unusual magnetic fields around Uranus and Neptune, which harbor vast water reserves deep within. Researchers now report that its structure is far more disordered than previously thought, blending face-centered cubic sections with hexagonal close-packed layers, resulting in an irregular hybrid rather than a uniform crystal.
Past studies suggested simpler setups, such as body-centered or face-centered cubic patterns for the oxygen atoms. However, advanced experiments have revealed the reality's complexity. Using the Matter in Extreme Conditions instrument at the Linac Coherent Light Source in the United States and the High Energy Density-HIBEF setup at the European XFEL, teams compressed water beyond 1.5 million atmospheres and heated it to thousands of degrees Celsius. X-ray laser pulses captured atomic snapshots in femtoseconds, confirming the mixed structure aligns with sophisticated simulations.
These findings echo the diversity of ordinary ice's phases, highlighting water's unpredictable nature under duress. The results bolster models of ice giant evolution, which may be prevalent across the universe. Over 60 scientists from Europe and the United States collaborated, funded by the German Research Foundation and France's ANR. The study appears in Nature Communications.